mm/memory_hotplug.c: drop memory device reference after find_memory_block() [Linux 5.1]

mm/memory_hotplug.c: drop memory device reference after find_memory_block() [Linux 5.1]

This Linux kernel change "mm/memory_hotplug.c: drop memory device reference after find_memory_block()" is included in the Linux 5.1 release. This change is authored by David Hildenbrand <david [at] redhat.com> on Thu Apr 25 22:23:37 2019 -0700. The commit for this change in Linux stable tree is 89c02e6 (patch).

mm/memory_hotplug.c: drop memory device reference after find_memory_block()

Right now we are using find_memory_block() to get the node id for the
pfn range to online.  We are missing to drop a reference to the memory
block device.  While the device still gets unregistered via
device_unregister(), resulting in no user visible problem, the device is
never released via device_release(), resulting in a memory leak.  Fix
that by properly using a put_device().

Link: http://lkml.kernel.org/r/20190411110955.1430-1-david@redhat.com
Fixes: d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Pankaj Gupta <pagupta@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Arun KS <arunks@codeaurora.org>
Cc: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There is one line of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 mm/memory_hotplug.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0082d69..b236069 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -874,6 +874,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
     */
    mem = find_memory_block(__pfn_to_section(pfn));
    nid = mem->nid;
+   put_device(&mem->dev);

    /* associate pfn range with the zone */
    zone = move_pfn_range(online_type, nid, pfn, nr_pages);

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